1. Field of the Invention
The present invention relates to a very thin coaxial cable end-processing method and end-processed structure, which, when cutting a shield conductor, reduces damage to an inner insulator thereof.
2. Description of the Related Art
A very thin coaxial cable is used as a high-frequency/high-speed signal transmission and large-flexibility cable, such as a cable for connecting a notebook PC and a liquid crystal display, a cable for connecting a medical ultrasonograph body and a probe, etc.
The very thin coaxial cable has sequentially stacked from its center to outer side a center conductor, an inner insulator, a shield conductor, and a jacket. When connecting the very thin coaxial cable directly to a device, or attaching to a connector, an end of the very thin coaxial cable is processed to expose its center conductor and shield conductor at the end.
FIGS. 5A-5D show a conventional process for processing an end of plural very thin coaxial cables.
Referring to FIG. 5A, plural very thin coaxial cables 1 are arrayed at a desired array pitch, and in that arrayed state, fixed with an adhesive tape 6.
Referring to FIG. 5B, by applying laser light, the adhesive tape 6 and jacket 5 of the very thin coaxial cables 1 are cut in a processing portion at a desired distance from an end, and the adhesive tape 6 and jacket 5 at the end are pulled together and removed from the processing portion. This causes shield conductors 4 to be exposed from this processing portion to the end. The cut refers to making a cut therein.
Referring to FIG. 5C, by applying laser light, the shield conductors 4 are cut in a processing portion nearer the end than the processing portion of FIG. 5B, and the shield conductors 4 at the end are pulled in the end direction and removed from this processing portion. This causes inner insulators 3 to be exposed from this processing portion to the end.
Referring to FIG. 5D, by applying laser light, the inner insulators 3 are cut in a processing portion nearer the end than the processing portion of FIG. 5C, and the inner insulators 3 at the end are pulled in the end direction and removed from this processing portion. This causes center conductors 2 to be exposed from this processing portion to the end.
Performing the above process results in the shield conductor 4, inner insulator 3 and center conductor 2 being exposed at the desired lengths, respectively.
Refer to JP-A-2007-290013 and JP-A-2007-20342, for example.
However, when applying laser light to the shield conductor 4 to cut the shield conductor 4, the conventional end-processing method causes the laser light to reach the inner insulator 3 after cutting the shield conductor 4, leading to laser light energy absorption into the inner insulator 3, and therefore damage to the inner insulator 3.
The method by JP-A-2007-290013 is designed to apply plural laser light rays by varying their optical axis angles, to give laser power uniformly to the entire shield conductor wrapped around the inner insulator. However, this causes the problem that when cutting an outer conductor of one of plural coaxial cables arrayed, a laser optical axis may be blocked by coaxial cables on both its sides, therefore rendering it impossible to configure the cables at a narrow array pitch.
The method by JP-A-2007-20342 shifts focus position of laser light in a perpendicular direction to the laser-applying direction, thereby reducing the thermal effect on the inner insulator. General processing lasers have large enough focus depth relative to very thin coaxial cable diameter, to have little practical effect of reducing the thermal effect even by perpendicularly shifting focus position of laser light by the order of not more than the very thin coaxial cable diameter. The thermal effect is inevitable.